A plasma processing apparatus is used to manufacture an electronic device such as a semiconductor device. The plasma processing apparatus includes various types of apparatuses such as a capacitive coupling type plasma processing apparatus and an inductive coupling type plasma processing apparatus. In recent years, a plasma processing apparatus of a type of exciting a gas by using microwaves has been used.
Japanese Unexamined Patent Publication No. 2012-109080 discloses a plasma processing apparatus using microwaves. The plasma processing apparatus includes a microwave output device outputting a microwave having a bandwidth. The apparatus can stabilize plasma by outputting the microwave having a bandwidth.
Japanese Unexamined Patent Publication No. H6-267900 discloses an apparatus which pulse-modulates a microwave for exciting plasma. This apparatus can prevent instability of plasma so as to reduce an electron temperature and an ion temperature.